The ARS RCX board has an LM324N (quad op-amp) as part of the design.
These op-amps along with P1 (for AZ) and P2 (for EL) are use to adjust
the the attenuation or gain needed to bring the input voltage within
range of 8 bit ADC.
If you adjust below the half way point of P1/P2 you will attenuate the
input voltage, above the half way point you add gain to the input
voltage. At the half way mark you should get out what you put in - no
attenuation or gain.
The EL circuit is working fine. The AZ circuit only allows for
attenuating the input voltage. When adjusting P1 for the EL input
voltage it only allows adjusting from 0 to max (0.71v) over the entire
range of P1.
I haven't played with op-amps before and what knowledge I have is
several years stale, but it seems I'm not getting my reference voltage
to the op-amps to allow for upward (or gain) adjustment to 5v.
There is a missing resistor (R9) on the board. It appears to have been
cut from the PCB. This may be my missing link. Unfortunately, EA4TX
says he no longer has schematics for this revision of the board.
-Freeman, N5FPP
On Sat, 2004-06-19 at 04:11, SV1BSX wrote:
> Freeman,
> you can increase the output voltage of HD-73 from 0.71 V to 5 Volts by
> using a homebrew
> OP-Amp stage with x7 multiplier (7 x 0.71 = 4.97 Volts). Thus, the input of
> Op-amp takes a voltage range 0 - 0.71 Volts and the
> output of this stage giving 0-5 Volts. If you don't know how to design
> something like that, let me know.
>
> 73, Mak SV1BSX
>
> ----- Original Message -----
> From: "Freeman P. Pascal IV" <pascal@pascal.org>
> To: "amsat-bb" <amsat-bb@AMSAT.Org>
> Sent: Saturday, June 19, 2004 7:30 AM
> Subject: [amsat-bb] ARS rotor controller and the HD-73 rotor
>
>
> > Are there any list members who are using the ARS RCX AZ/EL boards with
> > an Alliance HD-73 rotor or any rotor that return less than 5V at max
> > range?
> >
> > My HD-73 only provides 0.71 volts at max range. This is well below the
> > needed 5V for returning a value of 255 from the 8 bit ADC. The best I
> > can get is a max value of 36. ARSWIN complains this is way to low for
> > use.
> >
> > If anyone has an HD-73, could I trouble them to send me the voltage they
> > read at full range between terminal #6 on the back of the control unit
> > and the case?
> >
> > Does anyone now how to resolve this problem? I have v3.2 of the RCX-AZ
> > board. The older RCX boards had P3 and P4 which allowed adjusting the
> > voltage up. The board I have has a jumper across P3. I suspect I need
> > to insert an appropriate value here.
> >
> >
> > -Freeman, N5FPP
> >
> >
> >
> > ----
> > Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
> > Not an AMSAT member? Join now to support the amateur satellite program!
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>
>
>
>
> ----
> Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
> Not an AMSAT member? Join now to support the amateur satellite program!
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----
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